Crawler

ABSTRACT

A rubber crawler having a specified rotation direction includes a crawler body and plural lugs. The plural lugs are provided at the crawler body, and extend at an angle to a crawler peripheral direction from an end portion on a central line side toward a crawler width direction outer side and toward an opposite side to a crawler rotation direction. In a cross-section of the lugs taken along the crawler peripheral direction, an angle formed between each apex side portion of tread-in-side wall faces on the crawler rotation direction side and an outer peripheral face is 90 degrees or greater, and is smaller than an angle formed between each apex side portion of a kick-out-side wall faces on the opposite side to the crawler rotation direction and the outer peripheral face.

TECHNICAL FIELD

The present invention relates to a crawler formed using an elasticmaterial.

BACKGROUND ART

A rubber crawler is described in Japanese Utility Model ApplicationLaid-Open (JP-U) No. H05-82773. The rubber crawler has lugs that extendin a straight line along the crawler width direction, formed atintervals along a crawler peripheral direction. The rubber crawler has aspecified rotation direction, and a lug wall portion on an opposite sideto the crawler rotation direction has a larger angle of inclination withrespect to the crawler forward direction than a lug wall portion on thecrawler rotation direction side.

SUMMARY OF INVENTION Technical Problem

However, although the rubber crawler of JP-U No. H05-82773 is capable ofexhibiting sufficient traction performance when driving on rough grounddue to the configuration of the lugs as described above, there is atendency for side-slip to occur.

An object of the present invention is to provide a crawler thatsuppresses side-slip while securing traction performance during drivingon rough ground.

Solution to Problem

A crawler of a first aspect of the present invention is a crawler thathas a specified rotation direction. The crawler includes a crawler bodythat is formed from an elastic material in an endless shape entrainedaround a drive wheel and a follower wheel, and includes plural lugs. Theplural lugs are provided at the crawler body, project out from an outerperipheral face of the crawler body, as viewed from a crawler outerperipheral side, are allocated to one side and another side in thecrawler width direction so as to be alternately disposed on progressionalong the crawler peripheral direction on each side of a central linepassing through a crawler width direction center, and extend at an angleto the crawler peripheral direction from an end portion on the centralline side toward a crawler width direction outer side and toward anopposite side to a crawler rotation direction. In a cross-section takenalong the crawler peripheral direction, an angle formed between eachapex side portion of tread-in-side wall faces on the crawler rotationdirection side and the outer peripheral face is 90 degrees or greater,and is smaller than an angle formed between each apex side portion ofkick-out-side wall faces on the opposite side to the crawler rotationdirection and the outer peripheral face.

Advantageous Effects of Invention

As explained above, the crawler of the first aspect of the presentinvention is able to suppress side-slip while securing tractionperformance during driving on rough ground.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view of a rubber crawler of an exemplary embodiment ofthe present invention, as viewed from the side (along a crawler widthdirection).

FIG. 2 is a perspective view including a partial cross-section of arubber crawler of an exemplary embodiment of the present invention.

FIG. 3 is a perspective view including a partial cross-section ofrespective cord layers of a rubber crawler of an exemplary embodiment ofthe present invention.

FIG. 4 is a plan view of a rubber crawler of an exemplary embodiment ofthe present invention, as viewed from a crawler outer peripheral side.

FIG. 5 is a side view of the rubber crawler of FIG. 4 as viewed from thearrow 5X direction.

FIG. 6 is a cross section taken along line 6X-6X of the rubber crawlerin FIG. 4.

FIG. 7 is a cross-section taken along line 7X-7X of the rubber crawlerin FIG. 4.

FIG. 8 is a cross-section taken along line 8X-8X of the rubber crawlerin FIG. 4.

DESCRIPTION OF EMBODIMENTS

Explanation follows regarding a crawler according to an exemplaryembodiment of the present invention.

As illustrated in FIG. 1 and FIG. 2, an endless rubber crawler 10,serving as a crawler, according to the exemplary embodiment of thepresent invention is what is referred to as a coreless type rubbercrawler that does not have a metal core, and has a specified rotationdirection.

As illustrated in FIG. 1, the rubber crawler 10 is employed entrainedaround a drive wheel 100 coupled to a drive shaft of a tracked vehicleserving as a vehicle body, and an idle wheel 102 that is attached to thetracked vehicle so as to be freely rotatable. Plural rollers 104,disposed between the drive wheel 100 and the idle wheel 102 and attachedto the tracked vehicle so as to be freely rotatable, roll against aninner circumference of the rubber crawler 10.

Note that the drive wheel 100 of the present exemplary embodiment is anexample of a drive wheel of the present invention, and the idle wheel102 and the rollers 104 of the present exemplary embodiment are eachexamples of a follower wheel of the present invention.

In the present exemplary embodiment, a peripheral direction (illustratedby the arrow CD in FIG. 2) of the endless rubber crawler 10 is referredto as the “crawler peripheral direction”, and a width direction(illustrated by the arrow WD in FIG. 2) of the rubber crawler 10 isreferred to as the “crawler width direction”. Note that the crawlerperipheral direction (synonymous with the length direction of the rubbercrawler 10) and the crawler width direction are orthogonal to each otheras viewed from an inner peripheral side or an outer peripheral side ofthe rubber crawler 10.

In the present exemplary embodiment, the inner peripheral side (the sidein the direction indicated by the arrow IN in FIG. 6) of the rubbercrawler 10 entrained in an annular shape (encompassing circular annularshapes, elliptical annular shapes, polygonal annular shapes, and thelike) around the drive wheel 100 and the idle wheel 102 is referred toas the “crawler inner peripheral side”, and the outer peripheral side ofthe rubber crawler 10 (the side in the direction indicated by the arrowOUT in FIG. 6) is referred to as the “crawler outer peripheral side”.Note that the arrow IN direction (the direction toward the inside of theannular shape) and the arrow OUT direction (the direction toward theoutside of the annular shape) in FIG. 6 indicate in/out directions ofthe rubber crawler 10 when in an entrained state (synonymous with athickness direction of the rubber crawler 10).

Note that although the present exemplary embodiment is configured suchthat the rubber crawler 10 is entrained around the drive wheel 100 andthe idle wheel 102, there is no limitation thereto. For example,depending on the layout of the drive wheel 100, the idle wheel 102, andthe rollers 104, the rubber crawler 10 may be entrained around one orplural rollers 104 in addition to the drive wheel 100 and the idle wheel102.

The drive wheel 100, the idle wheel 102, the rollers 104, and the rubbercrawler 10 entrained thereon configure a crawler traveling device 90(see FIG. 1), serving as a traveling section of the tracked vehicle.

As illustrated in FIG. 1, the drive wheel 100 includes a pair ofcircular disk shaped wheel portions 100A that are coupled to the driveshaft of the tracked vehicle. Outer circumferential surfaces 100B of thewheel portions 100A respectively contact wheel-rotated faces 16 of acrawler body 12, described later, and roll against the wheel-rotatedfaces 16. The drive wheel 100 causes drive force from the trackedvehicle to act on the rubber crawler 10 (described in detail later), andcirculates the rubber crawler 10 between the drive wheel 100 and theidle wheel 102.

The idle wheel 102 includes a pair of circular disk shaped wheelportions 102A attached to the tracked vehicle so as to be freelyrotatable. Outer circumferential surfaces 102B of the wheel portions102A respectively contact the wheel-rotated faces 16, and roll againstthe wheel-rotated faces 16. The idle wheel 102 is moved in a directionaway from the drive wheel 100 and pressed against the wheel-rotatedfaces 16 by, for example, a hydraulic pressing mechanism, notillustrated in the drawings, provided at the tracked vehicle. Tension(pull) in the rubber crawler 10 entrained around the drive wheel 100 andthe idle wheel 102 is maintained by pressing the idle wheel 102 againstthe wheel-rotated faces 16 in this manner.

The rollers 104 each include a pair of circular disk shaped wheelportions 104A attached to the tracked vehicle so as to be freelyrotatable. Outer circumferential surfaces 104B of the wheel portions104A respectively contact the wheel-rotated faces 16 and roll againstthe wheel-rotated faces 16. The weight of the tracked vehicle issupported by the rollers 104. Note that the idle wheel 102 and therollers 104 rotate following the rubber crawler 10 circulating betweenthe drive wheel 100 and the idle wheel 102.

Note that the rubber crawler 10 (crawler body 12) is entrained aroundthe drive wheel 100 and the idle wheel 102 under a specific tension.Accordingly, frictional force arises between the outer circumferentialsurfaces 100B of the drive wheel 100 and the wheel-rotated faces 16,transmitting drive force of the drive wheel 100 to the rubber crawler10, and circulating the rubber crawler 10 between the drive wheel 100and the idle wheel 102 such that the rubber crawler 10 travels.

As illustrated in FIG. 1 and FIG. 2, the rubber crawler 10 includes thecrawler body 12 configured by forming a rubber material, this being anexample of an elastic material, into an endless belt shape. Note thatthe crawler body 12 of the present exemplary embodiment is an example ofan endless belt shaped crawler body of the present invention. Theperipheral direction, the width direction, the inner peripheral side,and the outer peripheral side of the crawler body 12 of the presentexemplary embodiment respectively match the crawler peripheraldirection, the crawler width direction, the crawler inner peripheralside, and the crawler outer peripheral side.

As illustrated in FIG. 2 and FIG. 3, at intervals around the crawlerperipheral direction, the crawler body 12 is formed with plural rubberprojections 14 projecting out from an inner peripheral surface 12Atoward the crawler inner peripheral side. The rubber projections 14 aredisposed along a central line CL passing through the crawler widthdirection center of the crawler body 12. The rubber projections 14restrict movement of the wheels in the crawler width direction bycontacting the wheels (referring to the drive wheel 100, the idle wheel102, and the rollers 104) rolling against the wheel-rotated faces 16. Inother words, by contacting the wheels, the rubber projections 14 arecapable of suppressing relative movement of the rubber crawler 10 andthe wheels in the crawler width direction. Namely, the rubberprojections 14 are capable of suppressing lateral misalignment of therubber crawler 10 with respect to the wheels. Note that the rubberprojections 14 of the present exemplary embodiment are examples ofprojections of the present invention.

In the present exemplary embodiment, the rubber projections 14 are laidout on the crawler body 12 such that the crawler width direction centerof the rubber projections 14 is positioned on the central line CL;however, the present invention is not limited to such a configuration.It is sufficient to lay out the rubber projections 14 on the crawlerbody 12 such that part of the rubber projections 14 is positioned on thecentral line CL. For example, the crawler width direction center of therubber projections 14 may be shifted to one side or the other side inthe crawler width direction with respect to the central line CL.

As illustrated in FIG. 2 and FIG. 6, the respective wheel-rotated faces16 are formed extending along the crawler peripheral direction at acrawler width direction outer side of the crawler body 12, with therubber projections 14 interposed therebetween. The wheel-rotated faces16 are configured with flat profiles, and configure a portion of theinner peripheral surface 12A of the crawler body 12.

Note that although in the present exemplary embodiment configuration issuch that the faces between the rubber projections 14 and thewheel-rotated faces 16 on the inner peripheral surface 12A of thecrawler body 12 are in the same plane (at the same height in this case)as each other, the present invention is not limited to such aconfiguration. For example, the wheel-rotated faces 16 may be configuredso as to rise up more toward the crawler inner peripheral side than thefaces between the rubber projections 14, or may be configured so as tobe hollowed out toward the crawler outer peripheral side (aconfiguration provided with indentations).

Lugs

As illustrated in FIG. 1 and FIG. 2, plural lugs 18 are provided on thecrawler body 12 so as to project out from the outer peripheral face 12Btoward the crawler outer peripheral side. As illustrated in FIG. 4, thelugs 18 are allocated to one side (the left side in FIG. 4) and anotherside (the right side in FIG. 4) in the crawler width direction on eachside of the central line CL of the crawler body 12 so as to bealternately disposed on progression along the crawler peripheraldirection on the one side or the other side. For convenience, the lugs18 on the one side in the crawler width direction will be referred tobelow as the lugs 18L, and the lugs 18 on the other side in the crawlerwidth direction will be referred to below as the lugs 18R.

Note that in the present exemplary embodiment, the placement interval ofthe lugs 18L in the crawler peripheral direction is the same placementinterval as the placement interval of the rubber projections 14.Similarly, the placement interval of the lugs 18R in the crawlerperipheral direction is the same placement interval as the placementinterval of the rubber projections 14.

The lugs 18 extend from an inner side end 18A on the central line CLside thereof toward the crawler width direction outer side and towardthe opposite side to the crawler rotation direction side (at an angletoward the upper side in FIG. 4) so as to extend at inclination to thecrawler peripheral direction. Note that reference here to the “crawlerrotation direction” means the rotation direction of the rubber crawler10 when the tracked vehicle is driven (advances) (the arrow R directionin FIG. 4). Due to configuration as described above, the inner side end18A side of the lugs 18 makes ground contact before the outer side end18B side thereof. Note that reference here to the inner side end 18Ameans the inner side end on the central line CL side at the base portion18D of the lugs 18, and the outer side end 18B means the outer side endon the crawler width direction outer side at the base portion 18D of thelugs 18.

Moreover, as illustrated in FIG. 4, there is a larger angle on the acuteangle side to the crawler peripheral direction further to the crawlerwidth direction outer side of the lugs 18 than that on the central lineCL side thereof. Note that the lugs 18 in the present exemplaryembodiment are configured so as to extend in a straight line at an angleto the crawler peripheral direction, and to be bent partway along (a2-stage angled configuration). Each of the lugs 18 of the presentexemplary embodiment accordingly includes a tread-in-side wall face 18Ealso referred to as forward wall face 18E) and a kick-out-side wall face18F also referred to as rearward wall face 18F), described later, thatare each angled in 2-stages with respect to the crawler peripheraldirection. Note that the present invention is not limited to the aboveconfiguration. For example, the lugs 18 may adopt a multi-stage angledconfiguration with respect to the crawler peripheral direction (aconfiguration in which the tread-in-side wall face 18E and thekick-out-side wall face 18F are respectively angled in multiple stageswith respect to the crawler peripheral direction), or a configurationcurved in a curved line with respect to the crawler peripheral direction(a configuration in which the tread-in side wall face 18E and thekick-out side wall face 18F are respectively curved with respect to thecrawler peripheral direction).

As illustrated in FIG. 7 and FIG. 8, in a cross-section taken along thecrawler peripheral direction, the tread-in-side wall face 18E on thecrawler rotation direction side (in other words, on the tread-in-side)of the lugs 18 is angled (which has the same meaning here as tilted)with respect to the outer peripheral face 12B of the crawler body 12.More specifically, the tread-in-side wall face 18E is sloped at a fixedangle to the outer peripheral face 12B from the vicinity of an apexportion 18C of the lugs 18 to the vicinity of the base portion 18Dthereof. Moreover, an angle θ1 formed between the tread-in-side wallface 18E and the outer peripheral face 12B is 90 degrees or greater, butis smaller than an angle θ2, described later.

Moreover, in a cross-section taken along the crawler peripheraldirection, the kick-out-side wall face 18F, on the opposite side of thelugs 18 to the crawler rotation direction (in other words, on thekick-out-side), is angled (which has the same meaning here as tilted) in2-stages with respect to the outer peripheral face 12B of the crawlerbody 12. Specifically, the kick-out-side wall face 18F is angled withrespect to the outer peripheral face 12B at a fixed angle θ2 from thevicinity of the apex portion 18C of the lugs 18 to a lug projectionheight intermediate portion thereof, and is angled with respect to theouter peripheral face 12B at a fixed angle θ3 from the intermediateportion to the vicinity of the base portion 18D. The kick-out-side wallface 18F is set here such that the angle θ2, formed between an apex sideportion 18FA on the apex portion 18C side and the outer peripheral face12B, is larger than the angle θ3, formed between a base side portion18FB on the base portion 18D side and the outer peripheral face 12B. Theangle θ3 is set so as to exceed 90 degrees.

The angle θ1 of the tread-in-side wall face 18E of the lugs 18 issmaller on the outer side end 18B side than on the inner side end 18Aside of the lugs 18. Moreover, the angle θ2 of the kick-out-side wallface 18F of the lugs 18 is smaller on the outer side end 18B side thanon the inner side end 18A side of the lugs 18. Note that the angle θ3 ofthe kick-out-side wall face 18F may be the same on the outer side end18B side as on the inner side end 18A side of the lugs 18, or may besmaller on the outer side end 18B side than on the inner side end 18Aside thereof.

The angle θ1 of the lugs 18 is preferably set within a range of from 102degrees to 115 degrees, and the angle θ2 is preferably set within arange of from 118 degrees to 132 degrees, and the angle θ3 is preferablyset within a range of from 104 degrees to 118 degrees.

As illustrated in FIG. 4, lugs 18 that are adjacent to each other in thecrawler width direction (a lug 18L and a lug 18R) have inner side ends18A that respectively overlap with each other when viewed along thecrawler width direction. In FIG. 4, the range over which the inner sideends 18A respectively overlap when viewed along the crawler widthdirection as described above (the overlap range) is indicated by thelabel P.

As viewed from the crawler outer peripheral side, the inner side ends18A of lugs 18 that are adjacent to each other in the crawler widthdirection respectively overlap with a single rubber projection 14.Moreover, as viewed from the crawler outer peripheral side, the innerside ends 18A of lugs 18 adjacent to each other in the crawler widthdirection are respectively disposed at positions separated from eachother in the crawler width direction. Specifically, a length W1 along acrawler width direction between inner side ends 18A of respective lugs18 adjacent to each other in the crawler width direction is set so as tobe within a range of from 4% to 10% of a length W0 along the crawlerwidth direction of the crawler body 12.

The lugs 18 are set such that an angle α formed between an inner sidewall face 18G on the central line CL side thereof and an outerperipheral face 12B is within a range of from 110 degrees to 120degrees.

In the present exemplary embodiment, the lugs 18 are configured so as tohave left-right symmetry about the central line CL; however, the presentinvention is not limited to such a configuration. For example, the lugs18 may be configured so as to have left-right asymmetry about thecentral line CL.

Cord Layer

As illustrated in FIG. 3 and FIG. 5, a main cord layer 20, a first biascord layer 22, a second bias cord layer 23, and a protection cord layer28 are embedded in the crawler body 12 in that sequence from the crawlerinner peripheral side.

The main cord layer 20 is an endless belt shape, and is superimposed atthe crawler outer peripheral side of a body inner peripheral portion 12Cforming the inner peripheral surface 12A of the crawler body 12. Themain cord layer 20 includes main cords 20A extending along the crawlerperipheral direction. The main cords 20A are configured by pluralstrands twisted together. In the present exemplary embodiment, as anexample, the strands are formed by twisting together plural filaments;however, the present invention is not limited to such a configuration.The main cords 20A are covered in rubber.

Moreover, although in the present exemplary embodiment steel cordshaving excellent tensile strength are employed as the main cords 20A,the present invention is not limited to such a configuration, andorganic fiber cords configured by organic fibers (for example, nylonfibers, aromatic polyamide fibers or the like) may be employed as themain cords 20A, as long as they have sufficient tensile strength.

The first bias cord layer 22 is configured in an endless belt shape, andis superimposed on the main cord layer 20 at the crawler outerperipheral side thereof. The first bias cord layer 22 includes anendless belt shaped bias ply 24 formed by embedding bias cords 24A inbelt shaped rubber, such that the bias cords 24A extend at an angle withrespect to the crawler peripheral direction and plural of the bias cords24A lie side-by-side in the crawler peripheral direction. Note that thebias ply 24 of the present exemplary embodiment is an example of a firstbias ply of the present invention.

The second bias cord layer 23 is configured in an endless belt shape,and is superimposed on the first bias cord layer 22 at the crawler outerperipheral side thereof. The second bias cord layer 23 includes anendless belt shaped bias ply 26 formed by embedding bias cords 26A inbelt shaped rubber, such that the bias cords 26A extend at an angle withrespect to the crawler peripheral direction and intersect the bias cords24A, and plural of the bias cords 26A lie side-by-side in the crawlerperipheral direction. Specifically, the bias cords 26A are angled in theopposite direction to the bias cords 24A with respect to the crawlerperipheral direction. Note that the bias ply 26 of the present exemplaryembodiment is an example of a second bias ply of the present invention.

In the present exemplary embodiment, the bias cords 24A and the biascords 26A are configured by the same steel cords. The bias cords 24A andthe bias cords 26A employ steel cords with a smaller diameter than themain cords 20A, from the perspective of the bending flexibility of therubber crawler 10. Note that the present invention is not limited tosuch a configuration, and organic fiber cords configured by organicfibers (for example, nylon fibers, aromatic polyamide fibers or thelike) may be employed as the bias cords 24A and the bias cords 26A aslong as they have sufficient tensile strength.

The protection cord layer 28 is configured in an endless belt shape, andis superimposed on the second bias cord layer 23 at the crawler outerperipheral side thereof, and is superimposed at the crawler innerperipheral side of a body outer peripheral portion 12D forming the outerperipheral face 12B of the crawler body 12. The protection cord layer 28is formed by superimposing plural layers of endless belt shapedprotection plies 30 (two plies in the present exemplary embodiment).Note that the protection plies 30 in the present exemplary embodimentare examples of the protection plies of the present invention.

The protection plies 30 are formed by plural strands of protection cord30A that extend along the crawler width direction (in other words adirection orthogonal to the central line CL), that are arrangedside-by-side in the crawler peripheral direction, and that are embeddedin belt shaped rubber.

Due to the protection cords 30A extending along the crawler widthdirection, the protection cord layer 28 has high rigidity in the crawlerwidth direction, or, in other words, is not liable to deform in thecrawler width direction.

In the present exemplary embodiment, in a state in which the rubbercrawler 10 is not yet mounted to a wheel (namely, in a state in whichtension is not being applied), the protection cords 30A extend along thecrawler width direction. Note that reference here to “extend along thecrawler width direction” includes cases in which they are angled withrespect to the crawler width direction by about ±3 degrees.

Although in the present exemplary embodiment steel cords are employed asthe protection cords 30A in order to raise the rigidity in the crawlerwidth direction, the present invention is not limited to such aconfiguration, and organic fiber cords configured by organic fibers (forexample, nylon fibers, aromatic polyamide fibers or the like) may beemployed as the protection cords 30A as long as they have sufficientrigidity in the crawler width direction.

Moreover, as illustrated in FIG. 6, a thickness T1 of the body innerperipheral portion 12C on the central line CL is thicker than athickness T2 of the body outer peripheral portion 12D. Moreover, on thecentral line CL, the thickness T1 is preferably set to a thicknesswithin a range of from 35% to 45% of a thickness T0 of the crawler body12, and the thickness T2 is preferably set to a thickness within a rangeof from 16% to 26% of the thickness T0.

In the present exemplary embodiment, the main cords 20A are disposed ata central portion in the thickness direction (which means the same asthe crawler in/out directions) of the crawler body 12.

Next, explanation follows regarding operation and advantageous effectsof the rubber crawler 10 of the present exemplary embodiment.

In the rubber crawler 10, as illustrated in FIG. 7 and FIG. 8, in across-section taken along the crawler peripheral direction, the angle θ1formed between the apex side portion of the tread-in-side wall face 18Eand the outer peripheral face 12B is 90 degrees or greater, but issmaller than the angle θ2 formed between the apex side portion 18FA ofthe kick-out-side wall face 18F and the outer peripheral face 12B.Hence, traction is improved in the rubber crawler 10 since the forcecomponent of the driving force applied to the soil in the horizontaldirection when driving on rough ground is increased compared, forexample, to cases in which the angle θ1 is larger than the angle θ2.Moreover, even in cases in which the soil of the rough ground is a sandysubstance, by adopting the configuration described above, soft dirt canbe suppressed from being swept away from the area of the apex portion18C of the lugs 18 that makes contact with the soil, using thetread-in-side wall face 18E. This thereby enables sliding between theapex portion 18C and the soil to be suppressed, and secures traction inthe machinery body forward direction. This thereby enables tractionperformance to be secured by the rubber crawler 10 when driving on roughground.

On the other hand, in the rubber crawler 10, the lugs 18 each extendfrom the inner side end 18A on the central line CL side toward thecrawler width direction outer side, and toward the opposite side to thecrawler rotation direction at an angle with respect to the crawlerperipheral direction. Thus due to the projected surface area of the lugs18 in the crawler width direction being increased in the rubber crawler10 compared, for example, to cases in which the lugs 18 extend in astraight line along the crawler width direction, the resistance tolateral force in the crawler width direction is improved when driving onrough ground. The rubber crawler 10 thereby enables side-slip whendriving on rough ground to be suppressed.

Moreover, in the rubber crawler 10, in a cross-section of the lugs 18taken along the crawler peripheral direction, the angle θ3 formedbetween the base side portion 18FB of the kick-out-side wall face 18Fand the outer peripheral face 12B is 90 degrees or greater, but issmaller than angle θ2. Thus in the rubber crawler 10, the spacing in thecrawler peripheral direction between lugs 18 adjacent in the crawlerperipheral direction can be widened compared to cases in which, forexample, the angle θ3 is larger than the angle θ2. Thus in the rubbercrawler 10, earth and mud can be suppressed from becoming lodged betweenlugs 18 adjacent in the crawler peripheral direction, and due toincreasing the efficacy of earth and mud discharge, the lugs 18 reliablypenetrate into the earth and mud, and traction and resistance to lateralforce are further improved.

Moreover, in the rubber crawler 10, the angle θ1 of the tread-in-sidewall face 18E of the lugs 18 is smaller at the crawler width directionouter side (the outer side end 18B side) than at the central line CLside (the inner side end 18A side). Due to such a configuration, in therubber crawler 10, due to the force component of the driving forceapplied to the soil in the horizontal direction being increased at thecrawler width direction outer side, the traction performance whendriving on rough ground is effectively improved. Moreover, due to theabove configuration, when driving on rough ground, the lugs 18 readilypenetrate into the earth and mud, and traction and resistance to lateralforce are further improved.

Moreover, in the rubber crawler 10, due to the angle θ1 of thetread-in-side wall face 18E of the lugs 18 being set within a range offrom 102 degrees to 115 degrees, the traction performance when drivingon rough ground can be further improved. Note that in cases in which theangle θ1 is smaller than 102 degrees, earth and mud is difficult todislodge, and sufficient traction cannot be obtained. However, if theangle θ1 exceeds 115 degrees, then sufficient spacing cannot be securedbetween lugs 18 adjacent in the crawler peripheral direction, andsufficient traction cannot be obtained. Thus the angle θ1 is preferablyset within a range of from 102 degrees to 115 degrees.

In the rubber crawler 10, as illustrated in FIG. 4, the inner side ends18A on the central line CL side of each of the lugs 18 adjacent in thecrawler width direction respectively overlap with a single rubberprojection 14 as viewed from the crawler outer peripheral side. Thus inthe rubber crawler 10, the rigidity to bending at the areascorresponding to the rubber projections 14 is larger, and the rigidityto bending at the areas corresponding to between the rubber projections14 is smaller. Thus in the rubber crawler 10, due to the areascorresponding to between the rubber projections 14 at the sectionsentrained around the drive wheel 100 and the idle wheel 102 bending soas to have a curvature greater than that of the areas corresponding tothe rubber projections 14, mud lodged between the lugs 18 when drivingon rough ground can be dislodged starting from the areas correspondingto between the rubber projections 14.

In the rubber crawler 10, as viewed from the crawler outer peripheralside, each of the inner side ends 18A of the lugs 18 adjacent to eachother in the crawler width direction are disposed at positions separatedin the crawler width direction. Thus in the rubber crawler 10, sincethere are no projecting objects such as lugs 18 formed on the centralline CL, mud can be suppressed from becoming lodged in the crawler widthdirection central portion, and even if mud were to become lodged,dislodging of the lodged mud is facilitated.

Moreover, in the rubber crawler 10, each of the inner side ends 18A ofthe lugs 18 that are respectively adjacent to each other in the crawlerwidth direction overlap with each other when viewed along the crawlerwidth direction. Thus in the rubber crawler 10, due to being able toachieve a wide spacing between the inner side ends 18A of the lugs 18respectively adjacent to each other in the crawler peripheral direction,mud can be further suppressed from lodging in the central portion in thecrawler width direction, and even if mud does become lodged, dislodgingof the lodged mud is facilitated.

Moreover, in the rubber crawler 10, the angle of the lugs 18, on theacute angle side, to the crawler peripheral direction is larger at thecrawler width direction outer side than that on the central line CL sidethereof. Thus in the rubber crawler 10 the force component of thedriving force applied to the soil in the horizontal direction isincreased at the crawler width direction outer side of the lugs 18, andtraction is improved.

The rubber crawler 10 accordingly suppresses lodging of mud when drivingon rough ground, and improves traction performance.

Moreover, in the rubber crawler 10, the length W1 along the crawlerwidth direction between inner side ends 18A of lugs 18 respectivelyadjacent to each other in the crawler width direction is set so as to bewithin a range of from 4% to 10% of a length W0 along the crawler widthdirection of the crawler body 12. Hence in the rubber crawler 10, theoccurrence of mud lodging between each of the inner side ends 18A of thelugs 18 that are adjacent to each other in the crawler width directioncan be suppressed. Note that in cases in which the length W1 is lessthan 4% of the length W0, sufficiently effective mud lodging suppressionis not obtained. However, in cases in which the length W1 exceeds 10% ofthe length W0, due to the length of the lugs 18 along the crawler widthdirection being shorter, sufficient traction performance is notobtained. The length W1 is accordingly preferably set within a range offrom 4% to 10% of the length W0.

Moreover, in the rubber crawler 10, due to the angle α formed betweenthe inner side wall face 18G of the lugs 18 and the outer peripheralface 12B being set within a range of from 110 degrees to 120 degrees,occurrences of mud lodging between each of the inner side ends 18A ofthe lugs 18 can be further suppressed. Note that when the angle α issmaller than 110 degrees, sufficiently effective suppression of mudlodging between each of the inner side ends 18A of lugs 18 is notobtained. However, if the angle α exceeds 120 degrees, due to the lengthof the apex portions 18C of the lugs 18 along the crawler widthdirection being shorter, sufficient traction performance is notobtained. The angle α is accordingly preferably set within a range offrom 110 degrees to 120 degrees.

In the rubber crawler 10, the protection cord layer 28 formedoverlapping the plural protection plies 30 is disposed at the crawlerouter peripheral side of the second bias cord layer 23. Thus in therubber crawler 10, the speed with which cracking caused by externaldamage to the outer peripheral face 12B of the crawler body 12propagates to the first bias cord layer 22 and the second bias cordlayer 23 can be slowed. By extending the time until cracking reaches thebias cords 24A and the bias cords 26A in this manner, problems with thebias cords 24A and the bias cords 26A due to the penetration of waterfrom outside can be suppressed for a long period of time, and thedurability of the rubber crawler 10 is improved.

Moreover, in the rubber crawler 10, the first bias cord layer 22 issuperimposed at the crawler outer peripheral side of the main cord layer20, and the second bias cord layer 23 is superimposed at the crawlerouter peripheral side of the first bias cord layer 22. Hence the biasply 24 and the bias ply 26 are close to the main cord layer 20, enablingthe deflection amount of the bias cords 24A and the bias cords 26Aduring turning to be reduced. This thereby enables buckling of the biascords 24A and the bias cords 26A to be suppressed from arising. Theoccurrence of problems with the bias cords 24A and the bias cords 26Aarising due to such buckling can thereby be suppressed for a long periodof time, improving the durability of the rubber crawler 10. Moreover, asdescribed above, due to the bias ply 24 and the bias ply 26 being closeto the main cord layer 20, an action to prevent twisting of the maincords 20A can be effectively obtained, improving the directionality ofthe rubber crawler 10.

In the rubber crawler 10, due to the thickness T1 of the body innerperipheral portion 12C of the crawler body 12 being thicker than thethickness T2 of the body outer peripheral portion 12D, problems can besuppressed from arising in the body inner peripheral portion 12C thatreceives load from the drive wheel 100, the idle wheel 102, and therollers 104.

In the rubber crawler 10, the main cord layer 20 is the neutral axis ofbending for the sections entrained around the drive wheel 100 and theidle wheel 102. Thus by disposing the main cords 20A at the centralportion in the crawler body thickness direction, a balance can beachieved between compression force acting on the inner peripheralsurface 12A of the crawler body 12 and tension force acting on the outerperipheral face 12B. This thereby enables the durability of the crawlerbody 12 to be improved.

Although in the exemplary embodiment described above a configuration isadopted in which each of the inner side ends 18A of the lugs 18 that areadjacent to each other in the crawler width direction are respectivelydisposed at positions separated from each other in the crawler widthdirection, the present invention is not limited to such a configuration.For example, a configuration may be adopted in which each of the innerside ends 18A of the lugs 18 that are adjacent to each other in thecrawler width direction overlap as viewed from the crawler peripheraldirection.

Moreover, although in the exemplary embodiment described above the lugs18 extend angled in 2-stages with respect to the crawler peripheraldirection, the present invention is not limited to such a configuration.For example, the lugs 18 may extend in a straight line at an angle tothe crawler peripheral direction.

Moreover, although in the exemplary embodiment described above aconfiguration is adopted in which the main cord layer 20, the first biascord layer 22, the second bias cord layer 23, and the protection cordlayer 28 are embedded in the crawler body 12 in this sequence from thecrawler inner peripheral side, the present invention is not limited tosuch a configuration. For example, the sequence may be changed for eachof the cord layers, and the first bias cord layer 22, the second biascord layer 23, or the protection cord layer 28 may be omitted.

Although embodiments of the present invention have been explained bygiving exemplary embodiments thereof, these exemplary embodiments aremerely examples, and various modifications may be implemented within arange not departing from the spirit thereof. It also goes without sayingthat the scope of rights of the present invention is not limited bythese exemplary embodiments.

The disclosure of Japanese Patent Application No. 2014-083143 filed onApr. 14, 2014 is incorporated by reference in its entirety in thepresent specification.

All publications, patent applications and technical standards mentionedin the present specification are incorporated by reference in thepresent specification to the same extent as if the individualpublication, patent application, or technical standard was specificallyand individually indicated to be incorporated by reference.

The invention claimed is:
 1. A crawler that has a specified rotationdirection, the crawler comprising: a crawler body, that is formed froman elastic material in an endless shape, entrained around a drive wheeland a follower wheel; and a plurality of lugs that are provided on thecrawler body, that project out from an outer peripheral face of thecrawler body, that, as viewed from a crawler outer peripheral side, areallocated to one side and another side in a crawler width direction soas to be alternately disposed on progression along a crawler peripheraldirection on each side of a central line passing through a crawler widthdirection center, and that extend at an angle to the crawler peripheraldirection from an end portion on the central line side toward a crawlerwidth direction outer side and toward an opposite side to a crawlerrotation direction, wherein, in a cross-section of the lugs taken alongthe crawler peripheral direction, an angle formed between each apex sideportion of forward wall faces on the crawler rotation direction side andthe outer peripheral face is 90 degrees or greater, and is smaller thanan angle formed between each apex side portion of rearward wall faces onthe opposite side to the crawler rotation direction and the outerperipheral face, wherein, in a cross section taken along the crawlerperipheral direction, an angle formed between each base side portionformed at a position lower than a central portion of a lug projectionheight of the rearward wall faces of the lugs and the outer peripheralface is 90 degrees or greater, and is smaller than an angle formedbetween each apex portion of the rearward wall faces and the outerperipheral face; wherein the position lower than a central portion ofthe lug projection height forms an angle transition at the rearward wallfaces that is present at at least more than half of the length of thelug width direction.
 2. The crawler of claim 1, wherein, in across-section taken along the crawler peripheral direction, an angleformed between each apex side portion of the forward wall faces of thelugs and the outer peripheral face is set within a range of from 102degrees to 115 degrees.
 3. The crawler of claim 1, wherein, as viewedfrom the crawler outer peripheral side, the lugs extend in a straightline at an angle to the crawler peripheral direction and are bent at abent portion, a first acute angle is formed by the intersection of: (1)an extension line along a portion of each lug further toward the centralline than the bent portion, and (2) a line formed along the crawlerperipheral direction, a second acute angle is formed by the intersectionof: (1) an extension line along a portion of each lug further toward thewidth direction outer side than the bent portion, and (2) a line formedalong the crawler peripheral direction, and the first acute angle issmaller than the second acute angle.
 4. The crawler of claim 1, wherein,as viewed from the crawler outer peripheral side, spacings in thecrawler peripheral direction between base portions of adjacent lugs inthe crawler peripheral direction are larger at the crawler widthdirection outer side than at the central line side.